CHICAGO – In recent years public schools around the nation have been privatizing many support services, like custodial work or food preparation.

The idea is to save money, because private vendors promise to perform the services for less than the districts previously paid unionized employees.

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But savings are only realized if school administrators properly award contracts through competitive bidding, give companies an accurate work description to formulate bids, and properly monitor the work to make sure the terms of contracts are met.

When those things don’t happen, costs can soar out of control and taxpayers take the hit. The following are two examples, from Chicago and New York City.

In 2015, Chicago Public Schools signed a three-year contract with a custodial company called Aramark to help clean the district’s approximately 600 schools on a daily basis, according to WBEZ.org.

The contract called for the district to pay $64 million for the first year of the service, according to the news report. But the company billed the district $86 million over the first 11 months.

When confronted about the overage, CPS Chief Administrative Officer Tim Cawley seemed to indicate that the information was wrong.

“No, we know we’re saving money now. There’s no question about that,” he told WBEZ.org, even though records showed that the district had paid Aramark $71 million, which was already $7 million over budget with other bills yet to be paid.

The district then apparently admitted that expenses were higher than anticipated, because Aramark had planned to lay off 468 custodians and perform the work with less labor, the news report said. But complaints about cleanliness prompted the company to keep many of the employees on the job.

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That cost an extra $7.4 million.

The district also admitted it forgot to include some buildings when determining the square footage that had to be cleaned. That added another $7 million in cost, the news report said.

CPS is not the only big city school district that’s apparently paid too much for cleaning services.

In 2014, the New York City Comptroller announced the findings of an audit that revealed that absence of proper bidding or oversight of a Department of Education contract with a custodial supply company.

The Department of Education had a five-year contract with Strategic Distribution Inc. for $88.1 million to provide and deliver janitorial supplies, according to a press release from the comptroller’s office.

Before awarding the contract, the district was supposed to have a competitive bidding process involving more than one vendor. But if that happened, the Department of Education could not prove it.

“The evidence provided by DOE was insufficient to establish that it conducted a fully competitive contract award process, or that it performed an adequate price analysis before it awarded the contract to SDI,” the press release said.

“DOE could not produce original bid submission documents and gave inconsistent evidence of its bid solicitation and conflicting information regarding the bidding process.”

Auditors also determined that the DOE failed to properly or accurately record the total amount spent on custodial purchases during the audit period, which meant it could not request possible discounts on future orders, the press release said.

DOE also failed to monitor “performance indicators” which could have led to price reductions. Finally, DOE did not respond to complaints from custodians that would have helped track performance issues.

“As a result, there is a strong risk that the city will end up overpaying for supplies that are purchased,” the press release said.

“DOE’s failure to properly monitor the contract on an ongoing basis may have resulted in the payment of higher costs and supply shortages,” New York City Comptroller Scott Stringer was quoted as saying.

“Competitive vendor selection and effective contract supervision are both necessary to make sure that goods and services are provided at fair, competitive and reasonable prices to reduce waste and inefficiency and to increase public confidence in the procurement process.”